首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5835篇
  免费   401篇
  国内免费   21篇
耳鼻咽喉   39篇
儿科学   182篇
妇产科学   64篇
基础医学   938篇
口腔科学   149篇
临床医学   472篇
内科学   1092篇
皮肤病学   253篇
神经病学   822篇
特种医学   311篇
外科学   412篇
综合类   29篇
一般理论   1篇
预防医学   430篇
眼科学   130篇
药学   427篇
中国医学   13篇
肿瘤学   493篇
  2024年   2篇
  2023年   46篇
  2022年   68篇
  2021年   130篇
  2020年   111篇
  2019年   132篇
  2018年   147篇
  2017年   120篇
  2016年   142篇
  2015年   202篇
  2014年   224篇
  2013年   287篇
  2012年   485篇
  2011年   468篇
  2010年   284篇
  2009年   276篇
  2008年   417篇
  2007年   386篇
  2006年   380篇
  2005年   389篇
  2004年   330篇
  2003年   323篇
  2002年   319篇
  2001年   48篇
  2000年   41篇
  1999年   69篇
  1998年   85篇
  1997年   64篇
  1996年   51篇
  1995年   42篇
  1994年   30篇
  1993年   36篇
  1992年   8篇
  1991年   7篇
  1990年   13篇
  1989年   13篇
  1988年   14篇
  1987年   11篇
  1986年   11篇
  1985年   7篇
  1984年   6篇
  1983年   4篇
  1982年   5篇
  1981年   5篇
  1980年   3篇
  1979年   2篇
  1977年   2篇
  1975年   2篇
  1974年   3篇
  1968年   2篇
排序方式: 共有6257条查询结果,搜索用时 15 毫秒
991.
Chronic Helicobacter pylori infection has been identified as a major risk factor for the subsequent development of gastric carcinoma. On the basis of seroepidemiological studies the relative risk for infected persons was estimated to range between 3 and 6. Our study attempted to determine the relative risk of gastric carcinoma in H. pylori-infected individuals based on the histological evaluation of gastritis in gastric carcinoma patients in the light of a declining prevalence of H. pylori infection in Western countries. We histologically determined the H. pylori infection rate in 215 patients with early gastric carcinoma (tumor stage pT1), and compared it with that of 215 asymptomatic persons matched by age and sex who were tested by the 13C urea breath test. On the basis of these data an odds ratio of 16.7 (CI 9.6–29.1) was calculated for the relative risk of developing gastric carcinoma in H. pylori-infected people. The histological diagnosis of gastritis permits a separate risk assessment for patients with autoimmune gastritis, and by excluding these patients from the analysis we calculated an odds ratio for H. pylori-infected persons of 150 (CI 36.4–622.9). The endoscopic-histological diagnosis of H. pylori infection is associated with an increased risk of the subsequent development of gastric carcinoma of approximately 150-fold compared with H. pylori-negative patients who do not have chronic atrophic corpus gastritis of the autoimmune type (type A gastritis). Int. J. Cancer 73:837–839, 1997. © 1997 Wiley-Liss, Inc.  相似文献   
992.
IntroductionTumor biological factors of breast cancer (BC) such as hormone receptor (HR) status, HER2 status, and grade can differ in the metastatic cascade from primary to lymph node (LN) metastasis and to distant metastatic tissue. Systematic data regarding therapeutic consequences are yet limited.MethodsWe conducted a prospectively planned, retrospective cohort study comparing BC phenotype in tissue from primary tumors (PTs), locoregional LN metastases, and disease recurrence (DR). HR and HER2 as well as tumor grade in PTs and DR were obtained by a database search. No centralized biomarker testing was performed. The impact of changes in tumor biological factors on post-recurrence survival (PRS) and overall survival was analyzed.ResultsPriMet comprises 635 patients (LN tissue in 142 patients). Discrepancies for HR or HER2 status between PT and DR were observed in 18.7 and 21.6% of cases, respectively. For HR status, positivity of PT and negativity of DR was seen more often (13.2%) than vice versa (5.5%). For HER2 status, negativity of the primary and positivity of DR was seen more often (14.9%) than vice versa (6.7%). Discordance was more often observed between PT and LN metastasis compared to LN versus DR. However, numbers were small. Compared to concordant non-triple-negative (TN) disease, concordant TN disease showed significantly inferior PRS.ConclusionWe demonstrate receptor discordance to occur relatively frequently between PT, LN metastasis, and DR and to impact patient prognosis. However, clinical consequences of receptor discordance need to be drawn with caution considering clinical aspects as well as tumor biology.  相似文献   
993.
Eating disorder patients, especially those with anorexia nervosa, are experientially avoidant. This group of patients finds talking treatments difficult and many standard psychotherapeutic techniques are difficult to implement. This paper discusses why therapeutic writing might be a useful adjunct to the treatment of eating disorders. Different types of therapeutic writing exercises may be useful at different stages of treatment and might aid the therapeutic process in different ways. The limitations of therapeutic writing are also discussed. Copyright © 2002 John Wiley & Sons, Ltd and Eating Disorders Association.  相似文献   
994.
Rhabdomyosarcomas bear a morphological and genetic resemblance to developing skeletal muscle. Apart from myogenic marker genes (bHLH factors, myosin, actin), cell adhesion molecules such as N-cadherin and N-CAM have been reported to be expressed both in rhabdomyosarcomas and during myogenesis. The present study demonstrates the expression of another cadherin, cadherin-11, in rhabdomyosarcomas and during differentiation of myoblasts in vitro: cadherin-11, a predominantly mesenchymal cell adhesion molecule, is highly expressed in embryonal rhabdomyosarcomas and alveolar rhabdomyosarcomas, which do not bear the Pax-3–FKHR fusion previously described. Cadherin-11 is down-regulated in normal skeletal muscle and after myotube formation in vitro. The results of this study suggest that cadherin-11 might be involved in myogenesis and that rhabdomyosarcomas may re-express or fail to down-regulate cadherin-11. Since alveolar rhabdomyosarcomas bearing the t(2;13) translocation do not express cadherin-11, it is postulated that Pax-3 and cadherin-11 might be linked and involved in the same myogenic pathway. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
995.
996.
Despite growing school lunch availability in Germany, its utilization is still low, and students resort to unhealthy alternatives. We investigated predictors of school lunch participation and reasons for nonparticipation in 1215 schoolchildren. Children reported meal habits, parents provided family-related information (like socioeconomic status), and anthropometry was conducted on-site in schools. Associations between school lunch participation and family-related predictors were estimated using logistic regression controlling for age and gender if necessary. School was added as a random effect. School lunch participation was primarily associated with family factors. While having breakfast on schooldays was positively associated with school lunch participation (ORadj = 2.20, p = 0.002), lower secondary schools (ORadj = 0.52, p < 0.001) and low SES (ORadj = 0.25, p < 0.001) were negatively associated. The main reasons for nonparticipation were school- and lunch-related factors (taste, time constraints, pricing). Parents reported pricing as crucial a reason as an unpleasant taste for nonparticipation. Nonparticipants bought sandwiches and energy drinks significantly more often on school days, whereas participants were less often affected by overweight (OR = 0.66, p = 0.043). Our data stress school- and lunch-related factors as an important opportunity to foster school lunch utilization.  相似文献   
997.
Merkel cell carcinoma (MCC), an aggressive neuroendocrine skin tumor, is a polyomavirus-induced human cancer. To study the causal relationship of MCC carcinogenesis with the integrated Merkel cell polyomavirus (MCPyV) in detail, well-characterized MCC cell lines are needed. Consequently, in the current study, we established and characterized six MCPyV-positive MCC cell lines. Microarray-based comparative genomic hybridization revealed a stable genome carrying only a limited number of chromosomal gains and deletions. All cell lines expressed MCC markers Keratin-20 and neuron-specific enolase as well as truncated MCPyV-encoded large T antigen (LT). For five cell lines, we were able to identify the MCPyV-integration sites in introns of different genes. The LT-truncating stop codon mutations and integration sites were affirmed in the respective clinical patient samples. Inverse PCR suggested that three of the cell lines contained MCPyV genomes as concatemers. This notion was confirmed for the two cell lines with known integration sites. Importantly, our observation of distinct stop codon mutations in cell lines with concatemeric MCPyV integration indicates that these LT-truncating mutations occur before integration. In summary, we provide the detailed characterization of six MCPyV-positive MCC cell lines, which are likely to serve as valuable tools in future MCC research.  相似文献   
998.

Sirtuin 3 is a nicotinamide adenine dinucleotide dependent mitochondrial deacetylase that governs mitochondrial metabolism and oxidative defense. The demise in myocardial function following myocardial ischemia has been associated with mitochondrial dysfunction. Sirt3 maintains myocardial contractile function and protects from cardiac hypertrophy. The role of Sirt3 in ischemia is controversial. Our objective was to understand, under what circumstances Sirt3 is protective in different facets of ischemia, using an in vitro proof-of-concept approach based on simulated ischemia in cultured cardiomyoblasts. Cultured H9c2 cardiomyoblasts were subjected to hypoxia and/or serum deprivation, the combination of which we refer to as simulated ischemia. Apoptosis, as assessed by Annexin V staining in life-cell imaging and propidium-iodide inclusion in flow cytometry, was enhanced following simulated ischemia. Interestingly, serum deprivation was a stronger trigger of apoptosis than hypoxia. Knockdown of Sirt3 further increased apoptosis upon serum deprivation, whereas no such effect occurred upon additional hypoxia. Similarly, only upon serum deprivation but not upon simulated ischemia, silencing of Sirt3 led to a deterioration of mitochondrial function in extracellular flux analysis. In the absence of oxygen these Sirt3-dependent effects were abolished. These data indicate, that Sirt3-mediated myocardial protection is oxygen-dependent. Thus, mitochondrial respiration takes center-stage in Sirt3-dependent prevention of stress-induced myocardial damage.

  相似文献   
999.
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号